5,000 year-old spermatozoa in Quaternary Ostracoda (Crustacea)

Fossil spermatozoa are recorded for the first time in freshwater ostracods (small bivalved crustaceans) from Holocene sediments at sites in the United Kingdom and Germany. Exceptional conditions at these sites have resulted in the preservation of chitinous "soft parts", including limbs, the remains of Zenker's Organs (sperm pumps that are part of the male reproductive apparatus in cypridoidean ostracods) and spermatozoa from eight different species. Comparisons are made with spermatozoa from living ostracods and the implications of these discoveries for evolutionary studies of reproductive modes are discussed.     

Phytoremediation of aged petroleum sludge: effect of inorganic fertilizer

Phytoremediation is a promising new technology that uses higher plants to enhance biodegradation. Nutrient availability is an important factor governing the success of phytoremediation and can be regulated through the addition of fertilizer. A greenhouse study was conducted to assess the importance of nitrogen and phosphorus for the phytoremediation of petroleum sludge. Degradation of total petroleum hydrocarbons (TPH) was quantified for six fertilization rates and three vegetation treatments: bermuda grass [Cynodon dactylon (L.) Pers.], tall fescue (Festuca arundinacea Schreb.), and an unvegetated control. During the first 6 mo of the experiment, TPH declined by an average of 49% with no significant differences between treatments. After 1 yr, TPH degradation was significantly greater in both vegetated treatments with a mean TPH reduction of 68% for bermuda, 62% for fescue, and 57% for the unvegetated control. Degradation of TPH in the fescue and bermuda treatments was significantly lower in the treatments in which no fertilizer was added or N and P were added simply to maintain plant growth compared with the higher rates of fertilization. For this short-term, greenhouse experiment, optimal remediation was obtained by fertilization that produced a C to N to P ratio of 100:2:0.2.     

The evolutionary continuum of limb function from early theropods to birds

The bipedal stance and gait of theropod dinosaurs evolved gradually along the lineage leading to birds and at some point(s), flight evolved. How and when did these changes occur? We review the evidence from neontology and palaeontology, including pectoral and pelvic limb functional morphology, fossil footprints/trackways and biomechanical models and simulations. We emphasise that many false dichotomies or categories have been applied to theropod form and function, and sometimes, these impede research progress. For example, dichotomisation of locomotor function into ‘non-avian’ and ‘avian’ modes is only a conceptual crutch; the evidence supports a continuous transition. Simplification of pelvic limb function into cursorial/non-cursorial morphologies or flexed/columnar poses has outlived its utility. For the pectoral limbs, even the classic predatory strike vs. flight wing-stroke distinction and separation of theropods into non-flying and flying—or terrestrial and arboreal—categories may be missing important subtleties. Distinguishing locomotor function between taxa, even with quantitative approaches, will always be fraught with ambiguity, making it difficult to find real differences if that ambiguity is properly acknowledged. There must be an ‘interpretive asymptote’ for reconstructing dinosaur limb function that available methods and evidence cannot overcome. We may be close to that limit, but how far can it be stretched with improved methods and evidence, if at all? The way forward is a combination of techniques that emphasises integration of neontological and palaeontological evidence and quantitative assessment of limb function cautiously applied with validated techniques and sensitivity analysis of unknown variables.     

Chemical investigations of defensive steroid sequestration by the Asian snake Rhabdophis tigrinus

Rhabdophis tigrinus is an Asian natricine snake that possesses unusual defensive glands on the dorsal surface of its neck. These nuchal glands typically contain cardiotonic steroidal toxins known as bufadienolides, which are also abundant in the skin of toads. Feeding experiments demonstrated that toads consumed as prey are the ultimate sources of the bufadienolides in nuchal glands of R. tigrinus. Indeed, snakes on a toad-free Japanese island (Kinkasan, Miyagi Prefecture) lack these compounds in their nuchal glands, confirming that these snakes are unable to synthesize defensive bufadienolides. However, when snakes from Kinkasan are fed toads in the laboratory, they accumulate bufadienolides in their nuchal glands, indicating that they have not lost the ability to sequester defensive compounds from prey. In contrast, R. tigrinus from a toad-rich island (Ishima, Tokushima Prefecture) possess large quantities of bufadienolides, reflecting the abundance of toads from which these compounds can be sequestered. Feeding experiments involving gravid R. tigrinus demonstrated that bufadienolides can be provisioned to offspring so that hatchlings are chemically defended before their first toad meal. Maternal provisioning of bufadienolides can take place through two routes: by deposition in yolk and by diffusion in utero, even late in gestation. We applied bufadienolides to the surface of eggs from Kinkasan and found that the embryos are able to take up these compounds into their nuchal glands, demonstrating the feasibility of uptake across the eggshell. Female R. tigrinus provision bufadienolides to their offspring in direct proportion to their own level of chemical defense. By feeding toad-derived bufotoxins to R. tigrinus hatchlings, we determined that the sequestration of these compounds involves at least three types of modification: hydrolytic cleavage of suberylarginine side chains, hydroxylation, and epimerization.     

Radioactivity standards for environmental monitoring. II

The current environmental-monitoring-standards efforts of the low-level-radioactivity laboratory in the Radioactivity Group of the National Bureau of Standards are described. The calibration efforts include traceability programs, natural-matrix Standard Reference Materials, alpha-particle-emitting standards, and international radioactivity intercomparisons. New radiometrology efforts under development include a prototype radon-222 in water standard, γ-ray emission-rate measurement techniques in the 60-keV region, and atom-counting techniques for radioactivity measurements.     

An assessment of variation in molluscan grazing pressure on Hong Kong rocky shores

Several methods of assessment have been used to document variation in grazing pressure on temperate rocky shores, although often these methods are applied without consideration of local conditions or species. In this study, a comparison was made between abundance counts of inactive molluscan grazers at low tide, direct observations of grazer activity and distribution throughout day and night tidal cycles, and records of grazing marks on wax discs, for the mid-shore of Hong Kong. The abundance of grazers found during low-tide counts varied among dates, sites and species. This method, however, did not record all grazer species that day/night observations showed to migrate from the low shore with the rising tide. Low-tide counts, therefore, underestimate grazing pressure (number of active grazers per unit area) and grazer guild (number of species). Grazing marks on wax discs also recorded a greater number of species than the low-tide counts of inactive grazers, and included grazers that were seen to migrate up shore during day/night observations. Certain limpet species, however, avoided the wax and did not leave grazing marks, showing this method to also underestimate grazing pressure. All methods showed grazing pressure to be variable at spatial scales of tens of metres or less and also temporally variable between sampling dates. The sole use of either low-tide counts or wax discs is likely to underestimate grazing pressure, due to variation in shore topography and grazer foraging behaviour, especially on shores with a narrow tidal range such as in Hong Kong. To gain a more accurate assessment of total grazing pressure, it is suggested that recording of grazing marks on wax discs should be used in conjunction with direct day/night observations.     

Determination of Mark-Houwink Parameters and Absolute Molecular Weight of Medium-Chain-Length Poly(3-Hydroxyalkanoates)

Absolute molecular weight distributions were determined for different medium-chain-length poly(3-hydroxyalkanoates) (MCL PHAs) with predominantly 3-hydroxyoctanoate (PHO), 3-hydroxynonanoate (PHN) or 3-hydroxydodecanoate content. This is the first study to estimate the Mark-Houwink constants of these polymers in the commonly employed GPC carrier solvent tetrahydrofuran (THF). The absolute molecular weight averages were determined via triple-detector size exclusion chromatography and combined with analyses using various detectors. Unlike with the short-chain-length poly(3-hydroxybutyrate), PHB, uncorrected polystyrene calibration in THF provided a good estimate (within 10 %) of absolute MW values for these MCL PHAs, irrespective of side chain length. Weight-average MW values ranged from 172,000 Da for PHO to 18,200 for PHN with 30 mol% 3-hydroxyheptanoate, and dispersities of all samples were close to two. Melt viscosity data suggested an entanglement molecular weight around 8 × 10⁴ Da, significantly higher than most polymers.